There is some improvement in vehicle control, but the biggest impact was inside the engine. Controlling the vehicle at transonic speeds benefits a lot from simulation- control inversion is an example. When grid find pass the sound barrier, the flow through the holes of the grid becomes choked off by shockwaves, and the fin starts acting like it was solid and sideways. Since it's effectively pointed 90 degrees off, it acts like its reversed. Knowing when, how intensely, and how turning affects that is important. Simulation also helps you find unexpected places where flows may unexpectedly become super/subsonic and cause torque. Experimenting at these speeds is... hard.
Simulation inside the engine can find resonances, show where shockwaves propagate, and show you how to build injectors (pressure, spray etc) so they are less affected by the path of reflections. Optimizing things like that smoothly along a range of velocities and pressures without a computer is not very feasible, and you need a minimum of computing power before you start converging to accurate results. The unpredictability of turbulence means low-resolution simulations will behave very differently.
Simulation inside the engine can find resonances, show where shockwaves propagate, and show you how to build injectors (pressure, spray etc) so they are less affected by the path of reflections. Optimizing things like that smoothly along a range of velocities and pressures without a computer is not very feasible, and you need a minimum of computing power before you start converging to accurate results. The unpredictability of turbulence means low-resolution simulations will behave very differently.